Abstract
multiple quantum wells were modulation doped with indium donors compensated by nitrogen acceptors so that the two-dimensional electron concentration in the wells could be varied from near 0 up to by optical pumping. In zero field at the optical absorption spectra show trion and exciton (X) resonance peaks at low with an electron-exciton scattering wing extending to high energy from the exciton resonance. At the highest the spectrum evolves towards the single asymmetric peak traditionally associated with the many-body “Fermi edge singularity” but its total integrated intensity remains almost constant, in agreement with recent few-body theories of the optical response at Under magnetic field at sharp and X resonance peaks are seen as well as a broad band Z situated about (the electron cyclotron energy) higher in energy. Band Z is attributed to a known exciton-electron scattering process [Yakovlev et al., Phys. Rev. Lett. 3974 (1997)] where the electrons are magnetically quantized. In circular polarization, the X resonance attenuates rapidly with but the resonance grows almost as rapidly (“intensity sharing”) so that their intensity sum falls only slowly. In the X resonance also attenuates rapidly with and the Z band grows to compensate, with the intensity sum again falling only slowly. It is concluded that the spectrum evolution as varies from 0 to in CdTe is due to intensity sharing between the X and resonances and between these resonances and scattering processes. This is a low (and low model of the excitonic properties, where screening and phase-space filling contribute only to the decrease of the oscillator strength sums. As regards the samples’ luminescence properties, two series of phonon peaks seen in emission spectra are attributed to recombination of two-dimensional electrons with nitrogen acceptors that have migrated close to and into the wells.
- Received 7 December 2003
DOI:https://doi.org/10.1103/PhysRevB.69.235303
©2004 American Physical Society